ANSWER Namu,
When you are replacing the water line for the icemaker you will first turn off water. Once water is off, remove the lower cover of the back of refrigerator. Take water valve loose. The Water line is connected to a john guess compression fitting. When removing you will push in on the ring around the water line and pull out on hose. If there is the same type of fitting at the top then you would release the same way. If there is not, then you would have to cut the line below where it enters the back of refrigerator and use a coupling to connect the 2 lines together.